A microcolumn as a miniature electron column, which operates under the basic principle of a Scanning Tunneling Microscope (STM) and is based on an electron emission source and electro-optical parts having micro-structures, was first introduced in the 1980s. The microcolumn is fabricated by assembling micro-parts precisely, thereby minimizing optical numerical values and, therefore, constructing an improved electron column. A plurality of micro-structures is arranged and can be used for a multi-microcolumn having a parallel or series structure.
The microcolumn is a mechanical micro-structure that includes a micro-electronic lens and a deflector and has a high aspect ratio. In general, the microcolumn includes an electron emission source, a source lens, a deflector, and an Einzel lens.
For a microcolumn, the alignment and fastening of an electron emission source, a source lens and an Einzel lens are very important in the light of the performance of the microcolumn. With respect to such alignment and fastening of a microcolumn, a conventional microcolumn is disclosed in Journal of Vacuum & Science Technology B14 6, pp. 3792-3796, “Experimental evacuation of a 2020 mm footprint microcolumn”, which was published in 1996.
FIG. 1 is a perspective view of a conventional microcolumn, which shows the conventional microcolumn in which an electron emission source, a source lens, deflectors and an Einzel lens are aligned and fastened. An upper plate 2, along with a micro-positioner (not shown) located on the top of the upper plate 2, forms a member for supporting the electron emission source, and a through hole is formed at the center of the member to position the electron emission source 1 therein. A lower plate 5 used as a support member for accommodating the upper plate 2 and the lenses, as shown in FIG. 1, is fastened using upper bolts via four support bars 6. The source lens 3 is aligned with the electron emission source 1 and is attached to the top of the lower plate 5 through epoxy bonding or the like. The deflectors 4 are arranged to the right and left of the lower plate 5. Furthermore, the Einzel lens (not shown) is assigned and fastened to the bottom of the lower plate 5 to be opposite the source lens 3 in the same manner as the source lens. The upper and lower plate 2 and 5 are respectively provided with through holes at the central axes thereof so that an electron beam emitted from the electron emission source 1 can pass through the lenses and the deflector.
FIG. 2 is a conceptual view showing the operation of conventional electron columns, which illustrates the concept of the operation of the conventional electron column.
In FIG. 2-A, an electron beam B emitted from the electron emission source 1 passes through the holes of a source lens 3, is deflected by a deflector 4, and is focused on a sample by a focus lens 6. The above-described conventional microcolumn is inconvenient in that the assembly and use thereof are inconvenient due to the wiring of the deflector 4 and the wiring of the focus lens 6. Furthermore, the associated procedure is complicated.
FIG. 2-B shows an embodiment in which a deflector is eliminated by performing both focusing and deflecting using a deflector-type lens layer. This technology is disclosed in Journal of Vacuum & Science Technology B13(6), pp. 2445-2449, “Lens and deflector design for microcolumn”, and pp. 3802-3807, “The electrostatic moving objective lens and optimized deflection systems for Microcolumn”, which was published in 1995.
In the electron column of FIG. 2-B, a focus lens 6′ includes a deflector-type lens layer 6b, which will be described later (refer to the description of FIG. 4), in the central layer thereof, and performs focusing and deflector functions, instead of the deflector 4 of FIG. 2-A.